1. Field of the Invention
The present invention. relates to an electronic print-board apparatus capable of recording and issuing in paper such information as a meeting agenda and drawings that are written on a screen of the board, particularly, an electronic blackboard apparatus provided for the purpose of reducing time from the beginning to end of printing in the case that plain sheet paper is used as a printing medium. The print-board means a blackboard, whiteboard, chalkboard, or write-board etc.
2. The Related Art
An electronic print-board apparatus comprises a screen that is incorporated in a looped form in a board. Such information as letters and figures are recorded in the screen. The information recorded is printed and issued in recording paper when it is required. The printing operation comprises steps of revolving the screen for reading and storing the information on a surface of the screen by a CCD, for example, and printing it thereafter by means of a printing device.
In such electronic print-board apparatus, mainly from the viewpoint of costs of the apparatus itself and recording paper used, thermal paper is generally employed as a recording medium. Accordingly, in order to cope with the thermal paper, the printing device is often provided with a printing head of thermal head type that comes in contact with the surface of thermal paper as a standard specification.
The thermal paper is wound in a roll, and the roll is unwound and supplied to the printing head for printing when the printing device is actuated. Then, the paper is discharged, after printing, from a lower side of the board as a sheet of paper of a size containing a printing area.
However, in the case such thermal paper is employed as recording paper, the paper is relatively not sturdy in quality, and is easily curled due to its history of being wound in a roll, thus it is difficult to be clerically handled and filed. In addition, the thermal paper has a characteristic of being changed in color in the course of time. Therefore, information printed and issued in the thermal paper is often copied onto plain paper by a copying machine, resulting in waste of time and paper.
In the case of plain sheet paper is employed as recording paper in place of such thermal paper, there is no difficulty in filing and handling, and an image recorded by printing comes to be clearer. In an electronic print-board apparatus for use with such plain paper offers easier clerical handling and filing in comparison with one for use with thermal paper.
An important point in an electronic apparatus is to reduce time required for printing to issuing in recording paper letters and figures that are written in a screen as much as possible. In order to reduce the time, it is effective, for example, to revolve the screen for simultaneously initiate a reading operation of an image by an optical reduction system including a CCD and a printing operation by a printing device. In other words, by synchronizing initiation of reading of an image and initiation of printing in recording paper, the processing time can be remarkably reduced in comparison with such conventional method that a printing operation is initiated only after an entire printing area of the screen is scanned for reading.
In such constitution that operations of reading images on the screen and printing them are synchronized with each other, by timing such that the recording paper reaches a print starting position when the screen comes to an image reading position, displacement of images within the recording paper and non-printed parts are reduced, and images of a good quality can be printed in the recording paper.
In the case the thermal paper is provided in the form of a roll, the thermal paper is extended integrally in the form of a continuous band to the printing head. Thus, a feeding speed of the thermal paper to the printing head and a downstream side thereof can be maintained in a constant manner by properly controlling feeding rollers that are provided in a line. Therefore, a synchronous relation between initiations of the operations of reading images on the screen and printing them can be maintained in a relatively high level.
On the other hand, in the case plain sheet paper is employed as recording paper, the paper sheets are fed from a tray one after another. Thus, the recording paper is intermittently fed to the printing head. Therefore, time required for a leading end of the paper to reach the printing head may be varied by feeding conditions.
For example, in the case the tray containing the paper is provided with a pick-up roller for picking up the paper and a hopper for compressing the paper against the pick-up roller, a first one of paper sheets is nipped in a predetermined position between the pick-up roller and the hopper. Therefore, for the first sheet of recording paper, time to reach the printing head is maintained as it is predetermined.
However, a second sheet of paper fed in succession may enter a nip part between the pick-up roller and the hopper due to friction between the second sheet and the first sheet, and a distance to the printing head is, therefore, slightly reduced.
Accordingly, time for a leading end of the second sheet to reach the printing head is also reduced, and the print starting time is reached before the time of reading images on the screen. Thus, when there is a difference between the image reading time and the print starting time, images read may be printed in a displaced manner on the paper, or an edge portion of image may be non-printed.
As described, while the synchronous relation between the image reading and printing operations can be maintained in such apparatus that rolled paper as thermal paper is continuously fed in the form of a band, it is difficult to maintain the synchronous relation in an apparatus for use with sheet paper, and failures in printing tend to be caused as a result.